In the case where it is necessary to make measurements of physical parameters, such as the pressure of a fluid, in an explosive environment or in a zone in which the measurements run the risk of undergoing disturbances of electromagnetic origin, it may be desirable to make these measurements by optical means, in order to avoid using an electric current.
To make these measurements, use is made of optical sensors which execute a modulation or an attenuation of an optical radiation penetrating the sensor, as a function of the variations of the quantity to be measured.
Optical sensors are known, in particular, which include a support, an optical fiber and at least one element mounted on the support which is capable of moving on the support as a function of the variations of the physical quantity to be measured. The movements of the movable element, which includes an active surface in contact with a generatrix of the optical fiber of undulated form, permit the deformation of the optical fiber by reverse bending, with an amplitude which is a function of the instantaneous value of the physical quantity to be measured.
The optical fiber is fed at one of its ends in such a manner as to cause the propagation of optical radiation along the length of the fiber, and the intensity of the optical radiation and its attenuation at the exit of the fiber are measured.
This attenuation is dependent upon the amplitude of the deformation of the fiber by reverse bending, and thus upon the value of the physical quantity to be measured.
The devices making use of this measurement principle generally include a support on which elements are fixed which are capable of moving relative to one another as a function of the variations of the physical quantity to be measured which may be, for example, a stress, a pressure or a temperature.
A strain gauge is known, for example, of optical type which includes two elements which may be fixed on the component in which the strains are measured, and which include pins between which an optical fiber is intercalated. When the component is deformed, the relative movement of the elements executes, via the a deformation of the fiber by reverse bending which permits the measurement of the amplitude of the deformations and thus of the strains in the component.
Also known is a device for measuring physical or mechanical quantities such as strains, temperatures or pressures, which includes a support on which elements are fixed for the deformation of an optical fiber including undulated surfaces in contact with two external generatrices of the fiber.
These known gauges or sensors of the prior art do not have a compact and stable structure permitting their use in an effective manner in an industrial installation. Moreover, the measurements made are liable to lack sensitivity and reproducibility, especially in the case of sensors employed for pressure measurements.